This is an observational (review of records), retrospective (research activity that is performed after the events under the study have occurred), registry study where data was collected from 3 different registries sponsored or supported by Centocor. Registries are Centocor-sponsored Therapy Resource Evaluation and Assessment Tool (TREAT™) Registry of Crohn's Disease, and in the following two Centocor-supported registries the Consortium of Rheumatology Researchers of North America, Inc. (CORRONA) registry and the Infliximab RA Registry, a subset of the National Database Registry of Rheumatoid Arthritis (NDBRRA) and of the National Databank for Rheumatic Diseases (NDB). A registry is data collection in a real life physician-patient setting. Physicians prescribe medications for rheumatoid arthritis and/or Crohns disease in accordance with their usual clinical practice and then record this information and provide it to Centocor. For this registry study, Centocor collected data from 3 registries to evaluate the risk of getting lymphoma if you have rheumatoid arthritis and/or Crohns disease and you have taken infliximab. Patients who were in one of the 3 registries and had rheumatoid arthritis and/or Crohns disease and did not take infliximab were also evaluated. This registry study does not involve the use of any investigational drugs.